1. Field of the Invention
The present invention generally relates to a method for preventing a collision of an extended orthogonal code which uses an extended orthogonal code applying a hadamard code, and prevents an extended orthogonal code""s collision occurred by a duplicated address based upon a multi rate traffic among a plurality of subscriber channels, in a wideband code division multiple access wireless local loop (hereinafter referred to as a WCDMA-WLL) communication system. More particularly, it relates to a method for preventing a collision of an extended orthogonal code which effectively prevents an address collision among a plurality of channels in case that the channels having different data transmission speeds are simultaneously transmitted by using one WCDMA-WLL frequency.
2. Description of the Prior Art
Conventionally, in case that a plurality of subscribers transmit a digital data by using one frequency in a WCDMA-WLL system, an extended orthogonal code has been used to divide each subscriber channel, and specifically a hadamard code among several orthogonal codes has been used to divide the same.
In order to correspond to the increasing subscriber""s channel number, such an extended orthogonal code generates an extended orthogonal code corresponding to the number of subscribers on the basis of a basic orthogonal code, and discriminates each subscriber channel.
The prior art will now be described with reference to the accompanying drawings.
FIG. 1 is a block diagram of an extended orthogonal code generator by a general hadamard code generator;
FIGS. 2A-2G show an extended state of an orthogonal code using a hadamard code in each of extended degrees; and
FIG. 3 is a state diagram of an extended orthogonal code occurring a data transmission speed difference according to one example of the prior art.
In more detail, FIG. 2A is a 1st extended orthogonal code. The extended orthogonal code shown in FIG. 2A divides a digital data into only two data xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d, and simultaneously uses only one channel.
FIG. 2B is a hadamard 2nd extended orthogonal code. The 2nd extended orthogonal code shown in FIG. 2B divides a digital data into four data xe2x80x9c11xe2x80x9d, xe2x80x9c10xe2x80x9d, xe2x80x9c00xe2x80x9d and xe2x80x9c01xe2x80x9d, and thus simultaneously uses two channels.
FIG. 2C is a hadamard 4th extended orthogonal code. The 4th extended orthogonal code shown in FIG. 2C divides a digital data into eight data xe2x80x9c1111xe2x80x9d, xe2x80x9c1010xe2x80x9d, xe2x80x9c1100xe2x80x9d, xe2x80x9c1001xe2x80x9d, xe2x80x9c0000xe2x80x9d, xe2x80x9c0101xe2x80x9d, xe2x80x9c0011xe2x80x9d and xe2x80x9c0110xe2x80x9d, and thus simultaneously uses four channels. In the same manner, a hadamard 8th extended orthogonal code shown in FIG. 2D can use 8 channels simultaneously in one frequency. A hadamard 16th extended orthogonal code shown in FIG. 2E can use 16 channels simultaneously in one frequency. A hadamard 64th extended orthogonal code shown in FIG. 2G can use 64 channels simultaneously in one frequency.
Therefore, by extending the orthogonal code with a successive multiple, a plurality of subscribers increased by a code number of an extended degree can be accepted by the extended orthogonal code.
Referring to FIGS. 2A-2G, in order to easily explain the extended orthogonal code, a basic orthogonal code is indicated as H, the 2nd extended orthogonal code is indicated as Hxe2x80x2, the 4th extended orthogonal code is indicated as Hxe2x80x3, the 8th extended orthogonal code is indicated as Hxe2x80x2xe2x80x3, the 16th extended orthogonal code is indicated as H4, the 32th extended orthogonal code is indicated as H5, and the 64th extended orthogonal code is indicated as H6.
As the number of subscribers increases in WCDMA-WLL system, each subscriber may use a specific data transmission speed. That is, in case that one subscriber transmits a digital data with a transmission speed of 32 Kbps, another subscriber transmits a digital data with a transmission speed of 64 Kbps being double of 32 Kbps, or a still another subscriber transmits a digital data with a transmission speed of 128 Kbps being quadruple of 32 Kbps, a collision portion wherein the extended orthogonal codes for discriminating each subscriber channel are overlapped occurs by a transmission speed difference. Therefore, it is impossible to discriminate each subscriber channel, and an error occurs in a transmitted digital data.
The aforementioned example will now be described with reference to FIG. 3.
If 8th extended orthogonal code of FIG. 2D is used as a hadamard orthogonal code for discriminating each subscriber, and one subscriber uses a 1st matrix code among the 8th extended orthogonal codes as a channel address with a transmission speed of 32 Kbps, the remaining 7 matrix codes can be used by another subscriber.
In other words, subscribers who want to occupy a matrix code degree (or channel) later can use all of the remaining 7 matrix codes of the 8th extended orthogonal code, in case that the subscribers transmit a digital data with the same transmission speed as that of a subscriber first occupying a specific matrix code(or channel).
However, in case of using a transmission speed of 64 Kbps being. double of 32 Kbps, an extended orthogonal code to be overlapped with the first occupied extended orthogonal code occurs by a transmission speed difference between 32 Kbps and 64 Kbps.
Namely, if the 1st matrix code of 8th extended orthogonal code is employed with a transmission speed of 32 Kbps as shown in FIG. 3(a), and a 5th matrix code of 8th extended orthogonal code is employed with a transmission speed of 64 Kbps as shown in FIG. 3(b), an analysis result by a hadamard code of discriminating each matrix code or channel shows the same extended orthogonal code as shown in an oval circle symbol xe2x80x9cOxe2x80x9d of FIGS. 3(c)-3(e).
Accordingly, in case of transmitting a subscriber""s digital data with a transmission speed of 64 Kbps, both the 1st matrix code previously transmitting the digital data with the transmission speed of 32 Kbps and the 5th matrix code which may appear as the 1st matrix code, cannot be used as a channel.
As a result, the remaining 6 matrix codes excepting the 1st and 5th matrix codes, i.e., 2nd, 3rd, 4th, 6th, 7th and 8th matrix codes, can be used as a channel for discriminating a plurality of subscribers.
Also, if a still another subscriber wants to transmit a digital data with a transmission speed of 128 Kbps, the same extended orthogonal code appears as shown in the oval circle symbol xe2x80x9cOxe2x80x9d of FIGS. 3(c)-3(e).
By a portion to be overlapped with the 1st matrix code of 8th extended orthogonal code, it is difficult to discriminate each matrix code, so that 3rd, 5th and 7th matrix codes cannot be used as a channel for discriminating a plurality of subscribers, only 2nd, 4th, 6th and 8th matrix codes can be used.
As stated above, in the prior digital data communication technique for discriminating a plurality of subscribers by using the extended orthogonal code applying the hadamard code in the WCDMA-WLL system, if even one subscriber among the plurality of subscribers uses a digital data transmission speed different from that of another subscriber, a duplicated matrix code pattern occurs in a pulse pattern of the transmitted digital data.
As a result, in a digital data communication by a plurality of subscribers, the prior art occurs an error of a data communication, and destroys an orthogonal characteristic of each matrix degree in the extended orthogonal code functioning as an address for discriminating each channel.
Accordingly, the present invention is directed to a method for preventing a collision of an extended orthogonal code that substantially obviates one or more of the problems due to limitations and disadvantages of the conventional art.
It is an objective of the present invention to provide a method which transmits the digital data having a different transmission speed of a plurality of subscribers without an error, by using an extended orthogonal code.
More specifically, the objective of the present invention is to provide a method for preventing a collision of the extended orthogonal code in a WCDMA-WLL system, which prevents a collision among subscriber channels being occurred in discriminating a plurality of subscribers who respectively use a digital data having a different transmission speed.
To achieve the above objectives, in case that a plurality of subscribers transmit a digital data with a different transmission speed, the present invention previously deletes an extended orthogonal code""s matrix code occurring a collision in a matrix code list, does not select the matrix code occurring a collision, and thus prevents a collision among the plurality of subscribers.
A method for preventing a collision among the plurality of subscribers includes the steps of:
setting an initial value of a variable K indicating a matrix code to xe2x80x9c1xe2x80x9d;
checking an extended degree N of an orthogonal code;
checking a multiple M of a data transmission speed, and determining a range of a variable L;
allocating a Kth matrix code of an orthogonal code;
determining whether the allocated matrix code is a matrix code presently used or a deleted code from a matrix code list;
if the allocated matrix code is neither the matrix code presently used nor the deleted code, deleting (L*N)/M+Kth matrix code from the matrix code list; and
determining whether there is a matrix code request requiring other matrix code.
Additional advantages, objects and other features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.